Sensitive relay



Nov. 15, 1960 Filed April 30, 1958 FIG.2

FIG.4

BY Georg llll INVENOR. Fl 6 5 Fkbard 7773/7 er 4am a/2047. X

United States Patent SENSITIVE RELAY Richard T. Fisher, Cohasset, and George M. Pahud,

Needham, Mass., assignors to Sigma Instruments, Incorporated, a corporation of Massachusetts Filed Apr. 30, 1958, Ser. No. 731,935

11 Claims. (31. 200-87) This invention relates to electromagnetic structures and more particularly to structures of this character which are suitable for use as relays of the polarized type.

An object of the invention is the provision of a highly efficient polarized magnetic relay having a small number of parts and capable of being easily assembled.

Another object of the invention is to provide a relay which is capable of being assembled substantially without any removable fastening means, which frequently becomes loose after extended use of the relay.

Another object is to provide an improved bearing construction for pivoting the armature.

According to one embodiment of the invention the relay is symmetrical about a plane through the pivot of the armature and the magnet is polarized symmetrically with respect to the pivot. The armature is preferably pivoted at its center of gravity so that it is relatively insensitive to linear accelerations. paths through the end poles of the magnet and the ends of the armature is the same at each end of the armature, the relay will be balanced in a neutral position. In some instances, however, it may be desirable to bias the armature in a limit position and it is a feature of the invention to accomplish that result without the use of springs by providing a path of low reluctance at one end of the armature. In this way increased spring pressure does not have to be overcome as the armature is moved to its opposite position and therefore the full closing pressure of the magnetic circuit is available, making for stability as well as great sensitivity.

The center pivot of the armature permits the use of two sets of contacts, one set being closed when the armature moves in one direction and the other set being closed when the armature pivots in the opposite direction. This provides for positive closing action in each direction by movement of the armature and simplifies adjustments of the relay and contacts. Differential adjustments are thus unnecessary andv assembly of the relay with the parts properly adjusted is facilitated.

Other and further objects of the invention will become apparent upon reading the following specification together with the accompanying drawings forming a part hereof.

In the drawings:

Fig. l is a perspective view of one embodiment of the invention showing the frame partly broken away;

Fig. 2 is an end view partly in section;

Fig. 3 is an elevational View partly in section and with the frame partly broken away;

Fig. 4 is a fragmentary side view showing a modified construction of the armature for providing magnetic biasing I thereof;

Fig. 5 is a fragmentary view showing how the relay may be utilized to actuate a spring contact pile-upgand Fig. 6 is a fragmentary side elevation showing a modified construction of the pole pieces providing for magnetic bias of the armature.

Referring to the drawings in detail, there is shown an If the reluctance of the- 2,9fitl583 Patented Nov. 15, 1960 sets of electrical contacts, each located at one end of the relay. The relay comprises a coil 10 which may have a cylindrical magnetic core 12 extending therethrough and protruding beyond the ends thereof. At each end of the coil there is provided a large magnetic washer 14 which closely fits the core 12. The ends of core 12 are held by end pieces 16 which are L-shaped, being provided with inturned horizontally extending portions 18. End pieces 16 have a bifurcated portion comprising a pair of tongues 20 which may be bent to slope toward each other slightly so as to tightly engage the core 12 and hold it captive. The use of the large washers 14 engaging the surfaces of the end pieces 16 insures a magnetic contact of very high permeability.

A bar magnet 22 rests on the in-turned portions 18. The magnet is symmetrically polarized so that both ends have one polarity and the middle of the magnet is of the opposite polarity; for example, the ends may be N-poles.

and the middle of the magnet may be an Spole. A magnetic bar 24 is in contact with the magnet at the middle thereof and extends transversely across the magnet. Bar 24 has one or more indentations 26 in registry with similar indentations 28 in an armature 3t Armature 30 is in the form of a bar of magnetic material balanced about its pivot which is defined by ball bearings 32 formed preferably of non-magnetic material and spaced near the sides of the armature. The magnetic attraction of the bar magnet 22 holds the armature in proper bearing contact with the spaced balls which provide low friction bearings and which also keep the armature in accurate alignment. It will be apparent that other equivalent means may be used for pivoting the armature on the magnet. The elements so far described are held in assembled relationship by a frame 34 which may be formed of nonmagnetic metal. The frame comprises two side plates having downwardly projecting legs 35 which are weldedor otherwise secured to a non-magnetic metal base plate 36. At each end the frame 34 has a pair of ears 38 tightly engaging the end pieces 16. The frame also includes a plurality of punch-outs which extend inwardly into engagement with the magnet so as to hold it in position. The frame also includes the turned-in portions 42 on each side thereof slightly spaced below the armature 30. Thus, the frame holds together the coil 10 and its core as well as the washers 14 and the end pieces 16, and by means of the elements 443 and the frame maintains the magnet 22, the armature 30 and the pivoting means therebetween in an assembled relationship. Owing to the clearance between the portions 42 and the armature and to the fact that the armature is held against the ball bearings by the magnetic force, it is free to pivot through the necessary range.

Contact assemblies 44 and 46 are mounted on each end of the relay. Each contact assembly may include the usual contact spring pile-up (Fig. 5) or as illustrated in Figs. 1 to 3, each contact assembly may consist of a movable spring contact 48 consisting of a resilient leaf spring mounted on a terminal pin 49. Terminal pin 49, and other terminal pins to be referred to later, extend through and are fixedly mounted in an insulating base 50 attached to the frame plate 36. Each contact assem-' or if desired may be arranged to have a neutral position therebetween.

A contact actuating assembly 64 is fastened to thearmature 30 by any suitable means. The assembly 64 may comprise a pair of diverging push rods 66 having rounded ends 68 of insulating material engaging the con-;

tact springs 48. When current is passed through the coil in one direction it will create a flux through the core 12, magnet 22 and armature 30. This flux will be added to the flux produced bymagnet 22 and will cause the left hand end of the armature to swing up toward the pole piece 18, thereby moving the right hand spring contact 48 downward and permitting the left hand spring contact 48 to move upward. The forces of the two leaf springs 48 on the armature substantially balance each other so that the movement of the armature does not have to take place against a substantial resultant spring bias. When a current is passd through the coil 10 in the opposite direction the armature will swing in the opposite direction to close against the right hand pole piece 18. In this manner the contact assemblies may be selectively operated. When operated to either position the armature will remain magnetically biased to that position by virtue of the low reluctance path which forms across one-half of the magnet. A reversal of the current will reverse direction of closing of the contacts.

In some instances it may be desirable to maintain the armature in a biased position until the occurrence of an actuating current.

Fig. 4 shows one way of biasing the armature without the use of a biasing spring. The armature 70 is mounted as previously described, but one side 71 is made longer than the other, that is, the end 71 of the armature extends further from the pivot 32 than the other end. This has the principal effect of biasing the symmetry of the magnetic circuit so that flux paths are similar to what they would be in a symmetrical circuit with some current flowing in the coil. Mechanical leverage biasing effects, if any, are in addition to this magnetic bias. Armature 70 is beveled at 72 so as to keep it substantially mechanically balanced about the pivot. Application of a current of the proper polarity to coil 10 causes the armature to move from its biased position and to close against the other pole piece. The armature is not required to move against a constantly applied force of a biasing spring.

The construction shown in Fig. 6 illustrates how biasing may be accomplished in another way Without the use of a biasing spring. As shown in this figure, one of the portions 18 forming the pole faces is made shorter than the other as indicated at 74 so that the reluctance is greater at this end than at the other and the attraction of the permanent magnet will normally draw the armature to a biased position. Application of current to the coil in a direction to attract the end of the armature to the short pole face at 74 will cause the armature to swing in that direction. It is not necessary for the armature, however, to overcome an increased force as would be produced by a biasing spring. Thus the full force of the magnetic pull of the coil is available to hold the contacts closed in each position of the armature.

For purposes of illustration I have shown certain embodiments of my invention but it will be apparent to those skilled in the art that many modifications and variations thereof may be made within the spirit and scope of the claims.

What is claimed is:

l. A relay comprising a coil, a magnetic core extending through said coil, a pair of magnetic end pieces each having a portion engaging and holding one end of said core and having a flange at the lower end thereof, a permanent bar magnet supported on said flanges and magnetically held thereon, said magnet having poles of the same polarity at its ends and a pole of the opposite polarity at the middle thereof, a bar armature disposed below and extending along said magnet, means for pivotally mounting the armature at the middle thereof, a base for the relay, an electrical contact assembly including a movable contact arm mounted on said base below said magnet and armature, a member mounted on said armature and engaging said movable contact arm for actuating the same, and a frame mounted on said base and having portions engaging and supporting said end pieces, said coil and magnet carried thereby.

2. A relay according to claim 1, including a contact assembly at each end of the relay, including a resilient contact arm, the contact actuating member on the armature including a pair of push rods each engaging one of said resilient contact arms, the push rods and the resilient contact arms being arranged symmetrically with respect to the pivot, whereby the resilient contact arms impose substantially no torque on the armature and the armature remains magnetically biased to either of its closed positions by the permanent magnet.

3. A relay according to claim 1 wherein the pivotal mounting means for the armature includes a magnetic member located at the middle of said magnet and extending transversely thereof and having an indentation in its bottom face, said armature being reversely indented in the upper face thereof and bearing means located in the indentations of the armature and said magnetic member.

4. A relay comprising a solenoid, a magnetic core extending through said solenoid and beyond the ends thereof, a pair of magnetic end pieces each having a portion for tightly receiving and holding the respective end of said core, the lower ends of said end pieces extending horizontally toward each other, a permanent bar magnet supported on said lower ends, said magnet being magnetized along its length, an armature disposed below said magnet, means for pivotally mounting the armature on the magnet, a base, an electrical contact assembly including a resilient movable contact mounted on said base, a member mounted on said armature and engaging said movable contact of the contact assembly for actuating said movable contact, and a frame mounted on said base and having integral formations engaging and supporting said end pieces and having integral formations for holding said magnet on said lower ends of the end pieces.

5. A relay comprising a coil having a magnetic core and a pair of pole pieces, a permanent bar magnet mounted parallel to said core and interconnecting said pole pieces, said magnet being magnetized so as to have poles of the same polarity at its ends adjacent said pole pieces and a pole of opposite polarity at the middle thereof, an armature pivoted at approximately its center of gravity, a contact assembly at each end of the armature, the armature being longer on one side of the pivot than on the other side of the pivot and a portion of the armature on the longer side being removed to substantially balance it mechanically about its pivot so as to provide paths of different values of reluctance at the opposite ends of the armature.

6. A relay comprising a coil having a magnetic core and pole pieces at the ends thereof, a permanent magnet mounted parallel to the axis of the coil, bearing means having indentations therein spaced transversely of the coil and mounted adjacent to said permanent magnet and near the center thereof, said indentations being in a plane parallel to the face of the permanent magnet, an armature extending longitudinally of the coil and permanent magnet and having indentations therein lying in a common plane facing the indentations on the bearing member, and a pair of spaced balls mounted in said indentations, the magnetic force of the permanent magnet drawing the armature into contact with the bearing balls and holding the balls in said indentations and the armature in alignment with the coil and magnet while permitting limited pivotal movement of the armature on the balls.

7. A magnetic device having a magnetic circuit in cluding spaced pole pieces, permanent magnetic and electromagnetic means for producing flux at said pole pieces, and an armature pivoted at approximately its center of gravity and having its ends in operative proximity to the respective pole pieces, the ends of the arrnature and the ends of said pole pieces extending in substantially the same direction and overlapping difierent distances at opposite ends of the armature so as to provide paths of different values of reluctance at the opposite ends of the armature.

8. A relay having a magnetic circuit including spaced pole pieces, a winding associated with said circuit for producing variable flux therein and permanent magnetic means associated with said circuit producing flux of the same sign at each of said pole pieces, and an armature pivoted at approximately its center of gravity and having its ends in operative proximity to the respective pole pieces, the opposite ends of the armature and the ends of the respective pole pieces extending along each other for different distances at said opposite ends so as to provide paths of different values of reluctance at the opposite ends of the armature.

9. A relay having a magnetic circuit including spaced pole pieces, a winding associated with said circuit for producing variable flux therein, a permanent bar magnet extending between said pole pieces, an armature extending parallel with said bar magnet and having ends cooperating respectively with said pole pieces, and cooperating bearing formations between said bar magnet and armature permitting tilting movement of the armature with respect to the bar magnet about an axis approximately midway of the length thereof, said axis lying in a 6 plane common to the faces of the pole pieces and being transverse to the length of the armature, said bearing formations being maintained in close bearing relationship by the magnetic force of said permanent magnet.

10. A construction as claimed in claim 7 in which the bearing formations comprise means providing complementary facing indentations on the facing surfaces of the bar magnet and armature and antifriction elements in said indentations.

11. A construction as claimed in claim 10 in which at least two pairs of complementary indentations are provided spaced laterally of the width of the armature and bar magnet and in alignment in the transverse axis of tilting movement of the armature, the antifriction elements in the indentations comprising hard nonmagnetic bodies of circular cross-section.

References Cited in the file of this patent UNITED STATES PATENTS 2,344,809 Eaton Mar. 1, 1944 2,428,218 Herbst Sept. 30, 1947 2,455,049 Edwards et al Nov. 30, 1948 2,612,544 Fisher Sept. 30, 1952 2,702,841 Bernstein Feb. 22, 1955 2,718,568 Somers Sept. 20, 1955 

